1. Field of the Invention
This invention relates to rocket propelled vehicles such as missiles and, more particularly, to arrangements for steering such vehicles by a combination of thrust direction and steering fin control.
2. Description of Related Art
As military aircraft become faster and more maneuverable, there is increased need for faster and more maneuverable missiles with longer ranges to counter these threats. One method of increasing maneuverability of a missile is to use a steerable nozzle on the rocket motor to allow the direction of thrust to be controlled. This affords greater maneuverability than traditional movable aerodynamic fins alone can provide under low speed or very high altitude conditions when the dynamic pressure is low. The mechanism used to move the steerable nozzle is known as the nozzle actuator system. The nozzle actuator system usually is located around the nozzle and infringes on the volume one would like to fill with rocket fuel. If the overall dimensions of the rocket motor are fixed, the smaller the nozzle actuator, the more the room that is available for fuel. Thus, smaller nozzle actuators give the missile greater range.
A simplified actuation system for controlling a steerable missile nozzle is disclosed in U.S. Pat. No. 4,892,253 of John M. Speicher and Allan A. Voigt, two of the inventors herein. That system utilizes a pair of orthogonally oriented, elongated yoke plates which are actuated in unison to control the direction of a gimballed nozzle. The disclosure of U.S. Pat. No. 4,892,253 is incorporated herein by reference.
Nozzle actuators and similar steering systems for missiles and the like have been built, based on hydraulic, pneumatic and electromechanical control systems. For example, Pollak in U.S. Pat. No. 2,850,977 discloses a gimballed power plant in a jet propelled aircraft in which exhaust gases from the rocket propulsion motor are utilized to adjust the rocket motor axis relative to the flight axis of the aircraft by having gyro-operated rotatable fins positioned in the exhaust gas stream. Adjustment of these fins by the aerodynamic forces impinging on them causes movement of the propulsion motor relative to the vehicle axis.
The Tolson U.S. Pat. No. 3,200,587 describes a number of structural arrangements for shifting a rocket engine exhaust nozzle to shift the thrust axis from a position coincident with the central axis of the vehicle to various positions where it is laterally displaced from the central axis. Movement of the thrust axis from the center of gravity or vehicle axis applies torque to the vehicle to effect directional change.
The Kuhn, Jr. U.S. Pat. No. 3,073,630 discloses a particular design of rocket engine gimbal which is provided to control the thrust direction of a rocket engine, relative to a missile body, by pivoting the exhaust nozzle in the gimbal.
Other schemes using steerable propulsion systems for exhaust jet propulsion systems are disclosed in U.S. Pat. No. 3,237,890 of Thielman, U.S. Pat. No. 2,919,544 of Smith, Jr. et al, U.S. Pat. No. 3,908,908 of Johnson, U.S. Pat. No. 3,188,024 of Schneider, U.S. Pat. No. 2,704,331 of Stott et al, U.S. Pat. No. 3,142,153 of Hensley, U.S. Pat. No. 3,147,591 of McEwen, U.S. Pat. No. 3,659,423 of Lair et al, U.S. Pat. No. 4,281,795 of Schweikl, and U.S. Pat. No. 4,350,297 of Martin.
In the development of modern nozzle actuators for controlling steerable exhaust nozzles, electromechanical systems have become dominant because of their improved effectiveness, reliability and reduced weight. Electromechanical nozzle actuators conventionally involve motors and some type of speed reducer to transform the high speed, low torque motor motion into high torque, low speed nozzle motion. Extension of nozzle actuator systems to provide control of aerodynamic steering fins as well would further improve the performance, efficiency, and cost effectiveness of such missile control systems.